A software system developed by AT&T to do an optimal routing of its international circuits over the worldwide cable and satellite network is described. The planning environment is discussed, and the overall architecture is described. The formulation of the models and their capabilities are summarized. Results generated by this system are used in the planning of international circuit loadings and construction of international facilities. The system does optimal routing of circuits for international message telecommunications service between United States and foreign switches; it also routes custom-services circuits between customer premises. The system takes into account the satellite-loading agreement between COMSAT and AT&T.>